From a39ae7f285feb64aaa9fba199944b6d84c9a1cd8 Mon Sep 17 00:00:00 2001
From: Matthew Roeschke <10647082+mroeschke@users.noreply.github.com>
Date: Wed, 21 Sep 2022 09:59:47 -0700
Subject: [PATCH] BUG: to_datetime(tz_mix, utc=True) converts to UTC

---
 doc/source/whatsnew/v1.5.1.rst         |  2 +-
 pandas/_libs/tslib.pyx                 |  2 +-
 pandas/tests/tools/test_to_datetime.py | 24 ++++++++++++++++++++++++
 3 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/doc/source/whatsnew/v1.5.1.rst b/doc/source/whatsnew/v1.5.1.rst
index 9d40d9118db32..a308c3d89ad1a 100644
--- a/doc/source/whatsnew/v1.5.1.rst
+++ b/doc/source/whatsnew/v1.5.1.rst
@@ -15,7 +15,7 @@ including other versions of pandas.
 Fixed regressions
 ~~~~~~~~~~~~~~~~~
 - Regression in :func:`.read_csv` causing an ``EmptyDataError`` when using an UTF-8 file handle that was already read from (:issue:`48646`)
--
+- Regression in :func:`to_datetime` when ``utc=True`` and ``arg`` contained timezone naive and aware arguments raised a ``ValueError`` (:issue:`48678`)
 
 .. ---------------------------------------------------------------------------
 
diff --git a/pandas/_libs/tslib.pyx b/pandas/_libs/tslib.pyx
index 4d071793b3935..8a21711a86e05 100644
--- a/pandas/_libs/tslib.pyx
+++ b/pandas/_libs/tslib.pyx
@@ -531,7 +531,7 @@ cpdef array_to_datetime(
 
                     else:
                         found_naive = True
-                        if found_tz:
+                        if found_tz and not utc_convert:
                             raise ValueError('Cannot mix tz-aware with '
                                              'tz-naive values')
                         if isinstance(val, _Timestamp):
diff --git a/pandas/tests/tools/test_to_datetime.py b/pandas/tests/tools/test_to_datetime.py
index 7e698b7a6b83d..590e506fca899 100644
--- a/pandas/tests/tools/test_to_datetime.py
+++ b/pandas/tests/tools/test_to_datetime.py
@@ -2815,3 +2815,27 @@ def test_to_datetime_cache_coerce_50_lines_outofbounds(series_length):
 
     with pytest.raises(OutOfBoundsDatetime, match="Out of bounds nanosecond timestamp"):
         to_datetime(s, errors="raise", utc=True)
+
+
+@pytest.mark.parametrize(
+    "arg",
+    [
+        ["1724-12-20 20:20:20+00:00", "2022-01-01 00:00:00"],
+        [
+            Timestamp("1724-12-20 20:20:20+00:00"),
+            Timestamp("2022-01-01 00:00:00"),
+        ],
+        [datetime(1724, 12, 20, 20, 20, 20, tzinfo=timezone.utc), datetime(2022, 1, 1)],
+    ],
+    ids=["string", "pd.Timestamp", "datetime.datetime"],
+)
+@pytest.mark.parametrize("tz_aware_first", [True, False])
+def test_to_datetime_mixed_tzaware_timestamp_utc_true(arg, tz_aware_first):
+    # GH 48678
+    exp_arg = ["1724-12-20 20:20:20", "2022-01-01 00:00:00"]
+    if not tz_aware_first:
+        arg.reverse()
+        exp_arg.reverse()
+    result = to_datetime(arg, utc=True)
+    expected = DatetimeIndex(exp_arg).tz_localize("UTC")
+    tm.assert_index_equal(result, expected)